Investigation of behavioral, physiological, pharmacological and anatomical elements in the role played by mesodiencephalic components of the cat brain relative to excitation and inhibition of nociception. Work in progress at this time is primarily focused on just how the pulvinar complex does and may interact with the central gray, certain subthalamic areas and the posterior intralaminar system. Comparative differences between lesion, stimulation, and drug effects on peripheral, i.e., tooth pulp and radial nerve, versus centrally induced pain have been rather extensively pursued. Also, the interaction of emotionally (savage) associated aspects of some nociceptive states is under investigation in the pulvinar relative to known hypothalamic and central gray roles in such manifestations.